Fence Repair

/*Fence Repair
Farmer John wants to repair a small length of the fence around the pasture. He measures the fence and finds that he needs N (1<=N<=
20,000) planks of wood, each having some integer length Li (1 ≤ Li ≤ 50,000) units. He then purchases a single long board just
long enough to saw into the N planks (i.e., whose length is the sum of the lengths Li). FJ is ignoring the “kerf”, the extra length
lost to sawdust when a sawcut is made; you should ignore it, too.
FJ sadly realizes that he doesn’t own a saw with which to cut the wood, so he mosies over to Farmer Don’s Farm with this long board
and politely asks if he may borrow a saw.
Farmer Don, a closet capitalist, doesn’t lend FJ a saw but instead offers to charge Farmer John for each of the N-1 cuts in the
plank. The charge to cut a piece of wood is exactly equal to its length. Cutting a plank of length 21 costs 21 cents.
Farmer Don then lets Farmer John decide the order and locations to cut the plank. Help Farmer John determine the minimum amount of
money he can spend to create the N planks. FJ knows that he can cut the board in various different orders which will result in
different charges since the resulting intermediate planks are of different lengths.
Input
Line 1: One integer N, the number of planks
Lines 2..N+1: Each line contains a single integer describing the length of a needed plank
Output
Line 1: One integer: the minimum amount of money he must spend to make N-1 cuts
Input
3
8
5
8
Sample Output
34
注意： He wants to cut a board of length 21 into pieces of lengths 8, 5, and 8.
The original board measures 8+5+8=21. The first cut will cost 21, and should be used to cut the board into pieces measuring 13 and 8.
The second cut will cost 13, and should be used to cut the 13 into 8 and 5. This would cost 21+13=34. If the 21 was cut into 16 and
5 instead, the second cut would cost 16 for a total of 37 (which is more than 34).*/
/*题意：FJ需要修补牧场的围栏，他需要 N 块长度为 Li 的木头（N planks of woods）。开始时，FJ只有一块无限长的木板，因此他需要把无限长
的木板锯成 N 块长度为 Li 的木板，Farmer Don提供FJ锯子，但必须要收费的，收费的标准是对应每次据出木块的长度，比如说测试数据中 5 8 8，
一开始，FJ需要在无限长的木板上锯下长度 21 的木板（5+8+8=21），第二次锯下长度为 5 的木板，第三次锯下长度为 8 的木板，至此就可以将长
度分别为 5 8 8 的木板找出 */

#include<iostream>#include<algorithm>#include<queue>#include<stack>#include<cmath>#include<string.h>#include<stdio.h>#include<stdlib.h>using namespace std;int main(){    long long int sum;    int i,n,t,a,b;    while(~scanf("%d",&n))    {        priority_queue<int,vector<int>,greater<int> >q;        for(i=0;i<n;i++)        {            scanf("%d",&t);            q.push(t);        }        sum=0;        if(q.size()==1)        {            a=q.top();            sum+=a;            q.pop();        }        while(q.size()>1)        {            a=q.top();            q.pop();            b=q.top();            q.pop();            t=a+b;            sum=sum+t;            q.push(t);        }        printf("%lld\n",sum);    }    return 0;}